Mustang 2040 electrical

[K9]

I am trying to rescue a Mustang 2040 that has been sitting idle for a couple of years. I have replaced the stop solenoid because the previous one got hot and burst. I later found out that the starter relay was sticking and that appears to be what melted the solenoid due the increased current flowing through there. I have figured out the electrical system except for one circuit. Coming off the second neutral centering switch, one of the wires goes to the control module, the other goes to the starter relay. If I disconnect the wire (labeled 21B) I have 12 + volts coming from the nuetral switch. If I connect it, it goes to zero volts. If I roll the engine, with the nuetral switch connected, it is around 3 or 4 volts. I have replaced the starter relay, mainly because it was burning up the stop solonoid. Does anyone know how that part of the electrical system is supposed to work. I have the service and part diagram for this machine, both of which have the electrical diagram that I find to be excellent resources, but comes up short in the explaination on this topic. All other voltages are 12 + going to the control module, so I think this is something I need to understand. I have yet to hear it purr. I bought it on a gamble and so far, I am coming up snake eyes. Thanks